The present invention relates to silver halide photographic photosensitive materials and more particularly to ultra-high contrast roomlight photosensitive materials used in printing plate making industry.
Recently, improvement in efficiency of the contact work in the field of printing has been demanded owing to complication of prints and development of scanners. For this purpose, photographic films of low sensitivity of as low as about 10.sup.-4 -10.sup.-5 of that of conventional contact films have been developed and have been put to practical use as contact films handleable under roomlight (under white fluorescent lamp from which ultraviolet ray has been excluded), namely, roomlight photosensitive materials. Performances required for such roomlight photosensitive materials are as follows: They are handleable under roomlight for a long time and have not only a high sensitivity to a light source of printers, but also a sufficient maximum density having a contrast equal to or higher than that of conventional darkroom photosensitive materials.
A special developer called lith developer has been used for providing high contrast and sufficient maximum density in this technical field. The lith developer contains only hydroquinone as a developing agent and concentration of free sulfite ion is considerably reduced by using the sulfite (preservative) in the form of an adduct with formaldehyde not so as to restrain the infectious developability. Therefore, the lith developers have serious defects that they are highly susceptible to oxidation with air and cannot be stored for longer than 3 days.
In order to obtain high contrast and sufficient maximum density, U.S. Pat. Nos. 4,224,401, 4,168,977, 4,166,742, 4,311,781, 4,272,606, 4,221,857 and 4,243,739 disclose methods of using hydrazine derivatives. Since according to these methods, sulfites of high concentration can be added to the developers, stability of the developers against oxidation with air is markedly improved as compared with the lith development.
However, for exhibiting sufficient effect of hydrazine derivatives, developers of relatively high pH are needed and besides, processing at high temperatures is necessary for completion of the processing in a short time. Therefore, it has become possible to carry out the processing at low temperatures and relatively low pH by adding amine compounds such as alkylamines and alkanolamines to developers as described in U.S. Pat. No. 4,269,929. However, since processing temperature and pH of these developers are still higher as compared with those of generally used developing systems for rapid processing and furthermore, amine compounds are contained in the developers, amount of the silver halide which dissolves into the developer is large to cause stain with silver of automatic developing machines and of photosensitive materials processed therein.
Moreover, development inhibitors (especially, heterocyclic compounds having mercapto group) have the action to inhibit the dissolution of the silver halide into developer, but in order that a sufficient effect of hydrazine derivatives can be obtained, a large amount of development inhibitors cannot be added to the photosensitive materials as in the case of other photosensitive materials containing no hydrazine derivatives. In view of this point, too, amount of the silver halide which dissolves into the developer increases to cause stain with silver.
Furthermore, it is customary for one skilled in the art to increase the content of silver chloride in the silver halide emulsion (or to increase it to 100%) or to use fine grain emulsions for making possible the long-term handling under roomlight, namely, for lowering the sensitivity to white fluorescent lamp from which the ultraviolet ray has been excluded and for still affording a high-contrast and sufficient maximum density. However, this method also accelerates dissolution of the silver halide into the developer to cause stain with silver of the developing tank in the automatic developing machines, the developing racks and the photosensitive materials processed therein.
On the other hand, when silver halide photographic photosensitive materials containing a hydrazine derivative are processed under a specific condition, the hydrazine derivative extraordinarily accelerates the development and as a result, numerous pepper fogs occur, dot images become too thick to perform proper contact operation or negative thin lines are ruptured. The above-mentioned specific condition means mainly the processing with a developer which has been exhausted due to oxidation with air with lapse of time.
Furthermore, roomlight photosensitive materials are required to be able to be handled for a long time under safelight (white fluorescent lamp from which ultraviolet ray has been removed). The photosensitive materials containing hydrazine derivatives are lower in safety as compared with those which contain no hydrazine derivatives and in the case of the former photosensitive materials,.fogs are formed in the processing of normal period of time or dot area ratio increases considerably. Besides, compounds having a mercapto group are effective as inhibitors against the extraordinary development caused by hydrazine derivatives, but the roomlight photosensitive materials containing the compounds having a mercapto group are further inferior in safety against safety light and use of these compounds are not effective to solve the problems.
Nowadays, the prints in our everyday life include not only lines or letters, but also the combinations of lines or letters with photographic images. Furthermore, in addition to the prints of black and white colors or single color, those of full colors increase. In photomechanical process, a photographic image original is converted to a dot image original by a scanner (separated into the colors of the desired numbers in the case of color printing) and the dot image original and a line image original are put together and exposed and printed on one contact film photosensitive material. In this way, an original for printing is prepared. In the case of color prints, originals for four colors (or at least two colors) are prepared. Therefore, roomlight photosensitive materials are further required to have suitability for the above-mentioned color plate making. Technical points in color plate making and color printing will be explained below.
In color printing, lines called register marks are drawn at the peripheral portions of plates in order for the printing of four colors (or at least two colors) being able to be performed at correct position, and at the printing step, registration is effected by exactly fitting them for all of four colors (or at least two colors). The register marks will be explained. As shown in FIG. 1, the register marks are lines given around the image part (which finally becomes the print) and are used not only for registration, but also for showing the position to be folded or cut in bookbinding. If these do not meet in the respective plates, the prints considerably decrease in commercial value.
However, in the photographic photosensitive materials containing hydrazine derivatives, thin lines such as register marks are finely and sharply formed under proper exposing conditions as compared with thick lines because the nucleation infectious development with hydrazine derivatives is weak (this tendency is strengthened by reducing exposure since thin lines of negative are readily ruptured in the photosensitive materials of this type). Therefore, contact reversal photosensitive materials containing hydrazine derivatives have the problem that the register mark is apt to get out of position (inferior in registration) because it is thin and sharp. If the register mark gets out of position, of course, thin lines get out of position not only in peripheral portion, but also in the image portion and handleability is extremely inferior.
Furthermore, for roomlight photosensitive materials, it is demanded for realizing the plate making operation of the higher efficiency to shorten the vacuum contacting step carried out prior to exposing in a printer. In order to improve the performance to shorten the vacuum contacting step, use of a matting agent having a large particle size is effective. However, if the particle size is too large, the matting agent makes the silver halide emulsion layer locally thin or reduces quantity of light at the exposing step to generate pinholes. As a result, opaque time increases and efficiency of plate making operation rather deteriorates. The inventor have confirmed that when silver halide photographic photosensitive materials contain hydrazine derivatives, high-contrast images are obtained as mentioned above and furthermore, the pinholes generated frequently can be reduced. However, when a dye which reduces the sensitivity of photosensitive silver halide emulsions is added to the photosensitive emulsion layer or other hydrophilic colloid layers as in general roomlight photosensitive materials for inhibition of degradation of image quality caused by irradiation, since the irradiation is inhibited, the light does not reach the portion shaded by the large matting agent and non-black portions remain and many pinholes are generated even if hydrazine derivatives are contained. On the other hand, if the dye is not contained, sharpness of the images is lost due to degradation of image quality caused by the irradiation. Means for sufficient improvement has not yet been reported.
Furthermore, it is known that use of acylhydrazine compounds as described in U.S. Pat. Nos. 4,168,977, 4,224,401, 4,243,739, 4,269,929, 4,272,614 and 4,323,643 generate nitrogen gas during development treatment. This gas gathers in the film to form bubbles, which bring about uneven development to damage the resulting photographic images.